[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P12] Spatial development of subauroral polarization stream associated with a pseudobreakup: SuperDARN and Arase observations

*堀 智昭¹、細川 敬祐²、西谷 望¹、新堀 淳樹¹、三好 由純¹、寺本 万里子³、尾花 由紀⁴、行松 彰⁵、桂華 邦裕⁶、笠原 慧⁶、横田 勝一郎⁷、中村 紗都子¹、笠羽 康正⁸、熊本 篤志⁸、土屋 史紀⁸、松田 昇也⁹、笠原 禎也⁹、松岡 彩子¹⁰、風間 洋一¹¹、Wang S.-Y.¹¹、Tam Sunny, W. Y.¹²、Jun Chae-Woo¹、篠原 育¹³ (1.名古屋大学宇宙地球環境研究所、2.電気通信大学、3.九州工業大学、4.九州大学、5.極地研究所、6.東京大学、7.大阪大学、8.東北大学、9.金沢大学、10.京都大学・地磁気世界資料解析センター、11.台湾高等研究院、12.台湾成功大学、13.宇宙航空研究開発機構・宇宙科学研究所)

キーワード：地球、電離圏、磁気圏、サブストーム

This study investigates how subauroral polarization streams (SAPS) develop longitudinally and latitudinally in association with a pseudobreakup on the basis of simultaneous conjugate observations made primarily by Super Dual Auroral Radar Network (SuperDARN) in the ionosphere and the Arase and geosynchronous satellites in the inner magnetosphere. In the event of interest during the 2022 Fall SuperDARN-Arase campaign, SuperDARN observed that SAPS appeared and readily intensified at magnetic latitudes of ~67° to ~72° in the evening sector and then expanded azimuthally toward the dusk sector. A close examination shows that SAPS intensified in the dusk sector first at latitudes slightly higher than the ionospheric footprint of Arase situated in the same magnetic local time (MLT) sector, and subsequently the SAPS expanded toward lower latitudes and reached the Arase's footprint. Interestingly, Arase detected drifting clouds of energetic ions at each of the SAPS intensification and the subsequent equatorward expansion, while one of the Geostationary Operational Environmental Satellites (GOES) completely missed any signature of energetic ion injection, despite that the GOES was located at the same MLT but slightly (~0.5 R_E) inward of Arase. Considering the simultaneous occurrence of a pseudobreakup seen from ground imager and geomagnetic field data, the observations strongly suggest that intermittent injections of energetic ions occurred at a later MLT and have drifted westward through the Arase location, leading to the observed evolution of SAPS there by supplying downward field-aligned current to the subauroral region. As evident from the GOES observations, the injections did not reach the geosynchronous orbit probably due to a weak electric field associated with the pseudobreakup.